Saturday, April 30, 2011

Abstract: The first year of LHC data taking provided an integrated luminosity of about 35/pb in proton-proton collisions at sqrt(s)=7 TeV. The accelerator and the experiments have demonstrated an excellent performance. The experiments have obtained important physics results in many areas, ranging from tests of the Standard Model to searches for new particles. Among other results the physics highlights have been the measurements of the W-, Z-boson and t t-bar production cross-sections, improved limits on supersymmetric and other hypothetical particles and the observation of jet-quenching, elliptical flow and J/Psi suppression in lead-lead collisions at sqrt(sNN) = 2.76 TeV.

It still amazes me how much they accomplished in the first year alone, considering the technical challenges that something of this size can have. It is an astounding machine in many ways, and it will provide us some of the most profound knowledge during its lifetime.

Thursday, April 28, 2011

This report describes a new and elegant experiment by the Gisin group. In this experiment, they have 2 entangled photons. One goes to a detector, the other gets amplified and generate a lot of photons with the same polarization state. In essence, the large number of photons are now a "macro" photon that is still entangled with the first photon. What they are doing is a micro-macro photon entanglement. This large number of photon is then detected by the human eye.

Using a similar set-up to that of Sciarrino, Gisin and his team entangled two photons. One was sent to a standard photon detector, while the other was amplified using a machine that generated a shower of photons with the same polarization, thereby, in theory, generating a micro–macro entangled state.

But Gisin replaced the photon detector Sciarrino used for the light field with a human. The beam of light produced by the amplifier could appear in one of two positions, and the location of the beam reflected the polarization state of the photons in the field. Gisin and his team sat in the dark for hours, marking the position of the light spot over repeated runs of the experiment, for the first time seeing the effects of quantum entanglement with the naked eye.

But then, they decided to check this by measuring the photon before it gets amplified, thereby destroying the entanglement with the first photon. Strangely enough, they get a false positive result!

But there was a hitch. What Gisin's team saw was not micro-macro entanglement. Gisin had a nagging suspicion that the Bell test may not be valid for macroscopic objects, so he deliberately set up the experiment so that the state of the second photon was measured before it was amplified. According to the rules of quantum mechanics, this act of measurement would break the entanglement, meaning that the first photon and the light field could not be in an entangled state. The system should not have passed the Bell test.

So essentially, they argued that the micro-macro entanglement isn't that convincing due to some issues. So I'm not sure how to spin this.

Tuesday, April 26, 2011

With a few days left before takeoff, space shuttle Endeavour's last flight will carry with it the Alpha Magnetic Spectrometer that will, finally, turn the International Space Station into a scientifically-significant facility, rather than a glorious piece of orbiting "motel".

Scientists believe anti-matter exists, and they said the alpha magnetic spectrometerhas been packed away in the space shuttle Endeavour in search for it.

Er... hello? We don't just believe that anti-matter exists. We KNOW they do, or else the Tevatron has been colliding imaginary particles, and PET scans is based on hypothetical ideas.

Providing evidence for the existence of antimatter is NOT what the AMS is for. It is a lot more subtle than that. The AMS webpage (link given earlier in this blog entry) should tell you what it is for. News article like this does a disservice because it makes it sound as if antimatter is still something unverified, and that "scientists" merely "believe" in its existence.

Ever notice how parents line up around the block to get into the schoolhouse meeting that's to discuss the cellphone policy, the dress code, bullying or the teaching of evolution? But I don't ever recall any parental protests about mediocre TCAP or ACT scores.

Ballgames bring the crowds by the hundreds (if not thousands), but how many parents showed up on parent-teacher conference day? In my 14 years of teaching high-school math, I typically had a handful on those days, when I needed to see dozens.

But the saddest part of this article is the description of what happened when a physics high school subject was taught properly:

In January 2008, the News Sentinel published my Citizen's Voice column, in which I complained that the typical kid was a million times more interested in his vast entertainment and social worlds than he was any academics.

One of the 26 replies I got was from a guy who was sent to an East Tennessee high school to strengthen its physics program. He was from the Distinguished Professionals Education Institute, meaning that he was top-notch.

Upon investigating, he discovered that his physics enrollment was much higher than would be ordinarily expected, that the previous year the class was taught by a coach and that almost every kid got an A. Physics should be one of the hardest classes in any high-school's curriculum. If taught correctly, few will take it, and they'll expect to work very hard. If kids eagerly sign up for physics, then the class is probably a joke.

Well, our serious teacher taught his physics class the right way: homework, labs and (oh, my goodness!) rigor. By mid-October, he was removed from the class, so widespread and vehement were the complaints from students and (surprise) parents.

This, of course, is the reverse in countries such as China, Singapore, South Korea, India, etc. There, students and parents do not dare complain about a subject being taught as being too "difficult" or demanding.

I would love to hear the "excuse" being given by the schools and the parents for removing that teacher.

I get asked that question frequently. Whenever I do an outreach project with either high school or college students, or even sometime even when I talk to the general public, I often get asked the question on what I think was the most important thing that I learned in becoming a scientist, or in this case, a physicist.

Now, I've mentioned a while back that I believe that the transition from being a "student" to being a scientist is when you learn the difference between what is "interesting" and what is "important. This is because what is interesting need not always be important, and making that realization is the first step towards becoming a scientist. So certainly, that realization and the ability to distinguish between the two is an important lesson in becoming a scientist.

But is that the most important thing that I've learned in becoming a scientist? When students asked me that question, they often expect that I would say that learning quantum mechanics, or electromagnetism, etc. would be the most important thing. So it comes as a surprise to many when I told them what I believe is the most important thing that I learned in becoming a scientist: Learning To Learn!

One of the things about being a scientist is that we always have to learn new things all the time! There's always something that we haven't heard of, something that is new, something we have never quite fully understand, or something puzzling. You are always faced with tying to find out about something. What we have acquired along the way, starting from undergraduate years to graduate school to postdoctoral work, and even through our early careers, is the ability and skill to learn. I'm not just talking about reading a book or paper and trying to understand something. I'm talking about knowing WHERE to look, WHO to ask, WHAT do I need to do to understand that, HOW do *I* understand something? We all work in different ways. Knowing how I, personally, comprehend something is very important, because I have consciously tried to discover when I can make something click in my head, and when it can't. How the material is presented, how I organize my thoughts in my head, how I work things out on paper, etc. are all my own personal preferences and skills that I know help me to understand something. In other words, at some level, I know what makes me tick and how I can grasp something. To me, this is the most valuable and important thing I learned in becoming a scientist.

So why is this the most important thing I learned? Besides the fact of what I've mentioned earlier about scientist always having to learn new things, it is also an important factor career wise. Not many of us are lucky enough to know what we want to do, and get to do it. Often, we have to make career changes, often changing field of studies due to one reason or another. Switching fields is not as uncommon as one would think, and in such cases, you definitely are faced with new knowledge to understand and comprehend. This is where the ability to learn becomes invaluable because in many situation, you are almost starting from scratch. This is where the skill that you used to obtain that PhD could be employed to get you up to speed in another field. The subject matter may be different, but if you've honed your skills properly, it is the same set that you will need to use to learn the new subject matter. It certainly happened to me when I switched from condensed matter physics to accelerator physics.

So yes, learning how to learn is the most important thing I learned in becoming a scientist.

It's a rich mix that the theory of superconductivity has given us," he says, referring to concepts such as pairing and symmetry breaking as applied to topology. "All those ideas really have their deep roots in work on superconductivity and they've become dominant tools for fundamental physics.

The point that is being stressed here, and which I've repeatedly mentioned, is that it is no longer a valid point to labelled areas of study such as condensed matter physics as being "applied physics". The knowledge gained, especially on the theoretical aspect of it, is as "fundamental" as anything. It is plainly apparent here in the case of superconductivity, but it can easily be said about the physics of graphene, topological insulator, BEC-BCS crossover, etc. It is in this field where various aspects of quantum field theory comes to life with utmost clarity. It is not pure fallacy that Carver Mead would say that "... Nowhere in natural phenomena do the basic laws of physics manifest themselves with more crystalline clarity...." regarding superconductivity.

So if anyone claims that anything other than high energy/particle/astrophysics/string/etc. is merely "applied", show him/her this.

Thursday, April 21, 2011

Japan's Tohoku earthquake and tsunami in Japan have caused the world to reconsider nuclear energy and its place in global energy policy. The University of Chicago Alumni Association, in conjunction with Argonne National Laboratory and the Harris Energy Policy Institute, invite you to join us for a live discussion and simultaneous webcast that will explore the impact of nuclear energy, now and in the future. The discussion will explore the topic from a variety of perspectives, including climate and ecology, economics, history, policy, safety, and science and technology. The panel includes:

* Mark Peters, Deputy Director of Argonne National Laboratory (Moderator)
* Kennette Benedict, Executive Director of the Bulletin of Atomic Scientists
* Hussein Khalil, Director of the Nuclear Energy Division at Argonne National Laboratory
* Robert Topel, Isidore Brown and Gladys J. Brown Distinguished Service Professor in Urban and Labor Economics, Chicago Booth School of Business, and Director, University of Chicago Energy Initiative.

Wednesday, April 20, 2011

Q. Nearly 50 years after Richard Feynman gave these lectures, why are they still relevant today?

A. Feynman brought a level of insight, enthusiasm and trenchant wit to the exposition of the fundamental laws of physics that is unsurpassed. These lectures come from the height of his “pedagogical period,” shortly after he finished his “Feynman Lectures” books. As for why they are still relevant, I addressed that in one of my commentaries. Here is a quote from my commentary on the last lecture:
“The laws of physics that Feynman has been describing are just as fresh and powerful as they were in 1964, or indeed decades earlier, when they were first discovered. In contrast a 50-year-old lecture series in biology, chemistry, computer science or the social sciences would be of historical interest only. For better or worse, the laws of physics don't change (no matter how much we may sometimes wish they would). Now, as in Feynman's day, they form the basis of all the other sciences, and Feynman's explanations are as fresh as any lectures in a classroom today. From time to time, I've added some modern perspective, occasionally correcting one of Feynman's remarks that proved incorrect in later years.”

There are also people who I think follow the cult of "celebrity". A lot of people who have very little inkling of understanding of Stephen Hawking's work, for example, still buy his books and flock to his appearance as if he's a rock star. I would think that Feynman legend continues to grow even after his death, and that helps to cultivate more "cult" following.

Tuesday, April 19, 2011

I've mentioned Clifford Will's name before in my blog entries (see here and here). He is certainly one of our most preeminent expert in General Relativity.

PNAS March 29, 2011 issue has published his inaugural article, along with a wonderful profile of this distinguished physicist. It contains not only information about him, but we also get a bit of a history lesson on the experimental tests of General Relativity.

Monday, April 18, 2011

Several years ago (in fact, close to 10 years ago), we read about an amazing experiment that showed for the first time the gravitational quantum states done by using a neutron free fall experiment. Now long comes an experiment, almost 10 years later, that probed these quantum states, again using neutrons, but with an induced frequency in one of the plate[1].

The new work by the ILL team has added what is known as a piezoelectric resonator to the bottom plate; its purpose is to jiggle the bottom plate at a very particular frequency.

The researchers found that as they changed the bottom plate's vibration frequency, there were distinct dips in the number of neutrons detected outside the plates - particular, well-spaced "resonant" frequencies that the neutrons were inclined to absorb.

These frequencies, then, are the gravitational quantum states of neutrons, essentially having energy bounced into them by the bottom plate, and the researchers were able for the first time to force the neutrons from one quantum state to another.

This then could be used as an extremely sensitive device to measure gravity at atomic scale.

I think everyone working in the field, except for theorists, needs to be told that there are aspects of doing science that can be dangerous if one isn't paying careful attention. A simple rubbing of one's eye while doing laser alignment can cause an accidental exposure of one's eye to that laser light. Many things can go wrong, and many times, they do when one isn't properly trained or be made aware of of the hazards. Luckily, most of the accidents are minor, but some time, it takes only one mistake to result in such tragic consequence.

As an experimentalist, my main focus has always been the work. But luckily, even though it can be annoying, the constant hammering of safety issues and the hazards that I face each day while at work do result in my conscious awareness of what I do and how I do it. When you deal with something where a serious mistake can lead to a life-or-death situation, you tend to want all the information you can get before doing the work.

One would hope that with this latest accident, universities will pay even more attention on how graduate students are trained to safely do their work.

Saturday, April 16, 2011

This appears to be a very clever experiment. However, I still have a bit of a problem understanding it completely, and I haven't had time to read the actual paper. Still, some of you may want to read it ahead of me, and might even be able to provide a clearer explanation before I can get to it.

By placing an atom very close to a mirror, and having the atom emits a photon either away, or towards the mirror, physicists at Heidelberg University, TU Munich, and TU Vienna have shown a superposition of an atom that is moving simultaneously in two opposite directions.

“If the distance between the atom and the mirror is very small, it is physically impossible to distinguish between these two paths,” Jiri Tomkovic, PhD student at Heidelberg explains. The particle and its mirror image cannot be clearly separated any more. The atom moves towards the mirror and away from the mirror at the same time. This may sound paradoxical and it is certainly impossible in classical phyiscs for macroscopic objects, but in quantum physics, such superpositions are a well-known phenomenon. “This uncertainty about the state of the atom does not mean that the measurement lacks precision”, Jörg Schmiedmayer (TU Vienna) emphasizes. “It is a fundamental property of quantum physics: The particle is in both of the two possible states simultaneousely, it is in a superposition.” In the experiment the two motional states of the atom – one moving towards the mirror and the other moving away from the mirror – are then combined using Bragg diffraction from a grating made of laser light. Observing interference it can be directly shown that the atom has indeed been traveling both paths at once.

I still have trouble understanding how the interference pattern can infer the superposition motion of the atom. To me, the photon itself will "self-interfere" since each one of them are in superposition of both paths (i.e. emitted away from the mirror and emitted towards the mirror and gets reflected back). Thus, when combined, they will self-interfere, very much like the double slit. So why the need for the Bragg diffraction grating?

Like I said, I definitely need to read the paper, since I am obviously missing something here.

Still, being able to show the atom having that opposite motion simultaneously is amazing. It is very much like the Delft/Stony Brook SQUID experiments, where the supercurrent was moving in two opposite directions at the same time.

The solutions showed that waves are best transmitted when their frequency matches a "resonance" value for the nonlinear layers, but as with many nonlinear systems, this frequency depends on the wave's amplitude. However, the dependence is different for oppositely-directed waves because of the asymmetric set-up. So for some amplitudes, if identical waves come from opposite directions, only one of them can have the right combination of frequency and amplitude to be fully transmitted, while the other is largely reflected. They found similar results with larger numbers of nonlinear layers.

Because Lepri's system doesn't rely on harmonics, as the photonic crystal system did, it can transmit light much more efficiently, says Panayotis Kevrekidis of the University of Massachusetts at Amherst. The amount of light that makes it through depends on the properties of the nonlinear material, which means you can tune the system to block some or all of the light. "What the nonlinear medium allows you to do is create perfect transmission," Kevrekidis says.

And it appears from this article that the test to show this isn't going to be too complicated. So it shouldn't be too long for us to hear the first experiment on such a system.

Thursday, April 14, 2011

The tentative agreement on the US 2011 budget presented the most optimistic scenario that one could ever imagine in this climate. It is reported that the DOE Office of Science budget will be cut only by 0.6% from 2010 level, when compared to the originally-proposed 18%. One can hear a collective sigh of relief from not only the National labs, but also a lot of universities and industries that make use of the many user facilities within those labs.

However, this is only a temporary reprieve. We are already in the battle for the 2012 budget, and a lot of people, especially politicians of a certain persuasion, simply are ignorant of the value of basic research and how it affects the economy. This is a continuing effort and a continuing struggle to make people be aware of such impacts.

In particular, DOE-funded scientists are worried about the office's 2012 budget request, now before Congress. "It's been an educational year," Isaacs says. "We learned that the argument [about the value of basic research] is still on the table and that we still have to make that argument."

So if you had written to your representatives during this last budget debacle to support science funding, thank you! But please, do not let up your support for basic science research if you truly believe in it. Continue to write to your representatives and ask them to consider what drives our economy and how science research has been a major player in that.

Wednesday, April 13, 2011

If you've read this blog for any considerable period of time, you would have noticed that I've highlighted several of Robert Crease's articles from time to time. So now, instead of him writing an article about something, this article is all about him, the main behind the story. Read his infamous encounter with Richard Feynman.

“So we aren’t any closer to unification than we were in Einstein’s time?” Crease asked. He and Feynman had been discussing the Standard Model, a cornerstone of modern particle physics that is considered to be almost a theory of everything, but still quite there be- cause it leaves out principle subjects like general relativity.

“It’s a crazy question!” Feynman said in anger. “We’re certainly closer. We know more. And if there’s a finite amount to be known, we obviously must be closer to having the knowledge, okay? I don’t know how to make this into a sensible question…it’s all so stupid. All these interviews are so damned useless.”

It was at that point that Feynman got up from his desk and cut the inter- view off. Crease heard Feynman yell from the corridor, “The history of these things is nonsense! You’re trying to make something difficult and complicated out of something that’s simple and beautiful.”

For a philosopher, he isn't that bad in dealing with science (is that a back-handed compliment?). A lot of his writing, especially his historical accounts, are very informative and entertaining, and I've always look forward to those.

Tuesday, April 12, 2011

A confirmation of the initial good news out of the Soudan Mines. As reported earlier, fire broke out at the underground laboratory that housed several important research projects. This could potentially be disastrous to the only underground research facility in the US. Luckily, the damage so far appears to be minimal.

Although the fire cut short by a month tests on detectors for the follow-on experiment, SuperCDMS, for which Cushman is co-spokesperson, she says those engineering tests will be "declared done" and the physics run will start this summer as planned.

Several smaller experiments in the underground lab, such as dark-matter search CoGeNT (Coherent Germanium Neutrino Technology), still have to be checked to see if their detectors have been compromised by having tiny amounts of material deposited on them due to the warming.

The Main Injector Neutrino Oscillation Search, a detector for neutrinos beamed from Fermilab 735 km away, has to be dried and its electromagnetic coil and other parts assessed. The MINOS lab needs a good cleanup from the firefighting foam and debris that got pulled in with it.

Monday, April 11, 2011

Luttinger liquid is usually a property of correlated electron (fermion) systems when confined to 1D. But in this latest scheme, a proposal has been made to confined photons in 1D that could exhibit the same spin-charge separation of Luttinger liquids.

Thus the suggestion by Angelakis et al. [1] that spin-charge-separated Luttinger liquid behavior could occur for photons in a one-dimensional nonlinear medium opens the door to a host of potential new studies and applications of spin-charge separation in one dimension. The basic idea is to employ a one-dimensional nonlinear optical media with two species of atoms to create a gas of strongly interacting polaritons of two “types,” which will become the analogs of spin and charge. The proposal draws on earlier work by Chang et al. [6] in which it was shown that a regime of very strongly interacting polaritions could be achieved in a single-component one-dimensional nonlinear optical media. In the single-component case, the strongly interacting polariton system was shown to realize a Tonks gas, a strongly interacting system of bosons with contact (zero range) interactions [6], which has already been observed in cold atomic gases (as opposed to photons) of bosons [8, 9]. When the interactions in a system of bosons are very strong, particles tend to avoid the same spatial location, which mimics the Pauli exclusion principle for fermions. Of this effect, one sometimes says that the strong interactions have caused the boson system to “fermionize.” Once a one-dimensional bosonic system reaches this regime, the connection to interacting fermions becomes clear, and the mathematical descriptions of the low-energy behavior are identical.

With Endeavor's last trip into space, it will carry a very important piece of experimental equipment for the International Space Station that might make the ISS finally becoming an important scientific facility - the Alpha Magnetic Spectrometer.

The idea for the AMS came from Samuel Ting, a Nobel Prize laureate out of MIT. This article documents his "odyssey" to have this built.

Starting in 1994, he threw himself into a project he called the Alpha Magnetic Spectrometer (AMS), a device of nearly eight tons that would be attached to the International Space Station. Essentially a giant magnet for sifting apart the particles in cosmic rays, the AMS will look for evidence of the mysterious dark matter that some physicists believe makes up more than 80 percent of the matter of our universe.

It is quite an informative article, not just about the AMS, but also about Samuel Ting. It also conveyed a very fascinating story on the discovery of the J/psi particle, and how it is another one of those "Who Ordered That?" situation.

Sunday, April 10, 2011

This is an interesting Q&A with UIUC theorists Philip Phillips. While it focused mainly on his career path to how he got to where he is now, it also contains some insight into various issues in condensed matter physics, especially on how some condensed matter system can actually test other fundamental physics.

[In 1998, Argentinean physicist Juan] Maldacena made a conjecture in which he argued that there is a relationship between a strongly coupled quantum mechanical system and a gravitational system [that] is entirely classical Einsteinian gravity. So in fact, strongly coupled quantum mechanical systems that are charged are equivalent to a curved space-time with a black hole in it. We showed that if you just introduce some probe fermions and these probe fermions are coupled to the space-time in a particular way, that system looks identical to the normal [nonsuperconducting] state of high-temperature superconductors.

Others have used this mapping before. What we did that was new is that we used a particular interaction between the probe fermions and the black hole that is really irrelevant to the physics of the black hole but changes the physics at the boundary of the space-time [which is where the quantum mechanical theory lives]. No one suspected it.

With such a model, you can just forget about trying to figure out what the basic building blocks are, just go and solve this geometry problem and extrapolate it to what's going on at the surface of this geometry, and you'll see what the quantum mechanical system is doing.

Friday, April 08, 2011

The article is a bit misleading in the sense that it's saying that "Gravity wins". It really has nothing to do with gravity, but rather, conservation of momentum.

Say the guy has mass M, and the woman has mass m, with m < M. For simplicity sake, let's assume that they both had the same velocity (but in opposite direction) before the collision
Momentum before collision is
Mv - mv = (M-m)v
Momentum after collision is:
MV_f + mv_f
(I'm not making any assumption yet on the directions of the velocities after collision.)
Applying the conservation of momentum, we get
(M-m)v = MV_f + mv_f
This means that mv_f is
mv_f = (M-m)v - MV_f
or
v_f = (M-m)/m * v - (M/m) V_f
Now, from the video, V_f (the velocity of the man after collision) appears to be in reverse, but very small, so V_f is negative, but small. So the 2nd term in the last equation is negative, making the equation to be
v_f = (M-m)/m * v + (M/m) V_f
Now, if M is substantially greater than m, M/m >1, and so (M-m)/m is also >1.

This means that v_f, the velocity of the woman after collision is greater than v, the initial velocity. She will recoil after collision with a greater speed than when she came in. This is what happened in the video.

One can also add another assumption of elastic collision, assuming the exercise balls didn't absorb too much energy in the collision. But I think the point has been made here. :)

Which, of course, didn't preclude him from deciding if something is worth funding or not. That then calls into question on how he would decide such a thing if it is a science/technical field. Did he simply delegated it to his minions? Or did he not based on scientific/technical merits, but rather purely on political issues? This type of attitudes, and lack of knowledge, explains why there were really astoundingly silly actions that have taken place.

It is one thing to be ignorant of what you don't know. It is another to actually be PROUD of such ignorance. I am not surprised if a large percentage of current crop of politicians (Tea Party, anyone?) have equal view on science.

After that, I am certainly curious as to what else he would come out with out of this Berkeley project. But the bigger question here will be, will the Koch foundation continue to fund this project? It will look very bad for that organization to stop funding just because the initial result just didn't match what they had hoped for. Will the Republican party continue to call on him to more congressional hearing on this topic? Hum?

Wednesday, April 06, 2011

The results, if they hold up, could be a spectacular last hurrah for Fermilab’s Tevatron, once the world’s most powerful particle accelerator and now slated to go dark forever in September or earlier, whenever Fermilab runs out of money to operate it.

“Nobody knows what this is,” said Christopher Hill, a theorist at Fermilab who was not part of the team. “If it is real, it would be the most significant discovery in physics in half a century.”

It is way too soon to for something like this to have such profound impact and declarations. As stated in the news article, if it is real, the LHC would be able to spot this quite easily. So as exciting of a news this could be, we just need to step back a little bit, give it some time, and let the scientific process works itself out.

In the team's experiment, the beams of molecules are passed through three sets of slits. The first slit, made from a slice of silicon nitride patterned with a grating consisting of slits 90 nanometres wide, forces the molecular beam into a coherent state, in which the matter waves are all in step. The second, a 'virtual grating' made from laser light formed by mirrors into a standing wave of light and dark, causes the interference pattern. The third grating, also of silicon nitride, acts as a mask to admit parts of the interference pattern to a quadrupole mass spectrometer, which counts the number of molecules that pass through.

The researchers report in Nature Communications today that this number rises and falls periodically as the outgoing beam is scanned from left to right, showing that interference, and therefore superposition, is present.

A very, very clever experiment, and it shows that if one can maintain coherence, size really doesn't matter in the manifestation of quantum effects.

Geo-neutrinos are the (anti)neutrinos produced by the natural radioactivity inside the Earth. In particular, the decay chains of 238U and 232Th include six and four β− decays, respectively, and the nucleus of 40K decays by electron capture and β− decay with branching ratios of 11% and 89%, respectively. The decays produce heat and electron antineutrinos, with fixed ratios of heat to neutrinos (table 1). A measurement of the antineutrino flux, and possibly of the spectrum, would provide direct information on the amount and composition of radioactive material inside the Earth and so would determine the radiogenic contribution to the heat flow.

It's interesting that the article mentioned that the Earth emits mainly electron antineutrino, while the sun emits mainly electron neutrino. In light of the recent possible error in estimating the amount of electron antineutrino that is emitted from such nuclear reaction, I wonder if this makes the study of geo-neutrinos even more difficult. Or maybe the 3% difference doesn't matter.

Experiments that measure the rate of antineutrino production from the decay of uranium and plutonium isotopes have so far produced results roughly consistent with this theory. But the revised calculation1 accepted this week by Physical Review D suggests that it's not the whole story. While waiting for the Double Chooz neutrino experiment in France to become fully operational, Thierry Lasserre and his colleagues at the French atomic energy commission(CEA) in Saclay set out to check predictions of the rate of antineutrino production by nuclear reactors. They repeated a calculation first done in the 1980s by Klaus Schreckenbach at the Technical University of Munich, using more modern techniques that allowed them to be much more precise.

Their new estimate of the rate of production is around 3% more than previously predicted. This means that several generations of neutrino and antineutrino experiments have unknowingly missed a small fraction of the particles. "It was completely a surprise for us," says Lasserre.

A possible mechanism for the non-detection of these antineutrinos could be the possible oscillation into "sterile" neutrinos.

The result may be pointing to evidence of neutrinos and antineutrinos oscillating into a fourth kind of neutrino or antineutrino, a so-called 'sterile' version that doesn't interact with ordinary matter, says Carlo Giunti, a physicist at the University of Turin in Italy. Other experiments have previously seen evidence for sterile particles, including the Liquid Scintillator Neutrino Detector at Los Alamos National Laboratory in New Mexico and the Mini Booster Neutrino Experiment, or MiniBooNE, at Fermilab in Batavia, Illinois, and the search to confirm their existence is a hot area of physics.

With several neutrino experiments going online soon, one would think that this would be something that might looked at. So stay tuned!

Monday, April 04, 2011

It is very seldom that I read something and then say "Whoa! This person is writing exactly what I have been thinking of, or what I've been saying all along!" Maybe it is why I found this preprint so entertaining to read.

I don't know if this has been submitted anywhere for publication. It doesn't matter. It is still something that should be read. Z. K. Silagadze from the Budker Institute wrote a very illuminating (and, of course, entertaining) article on how our insistence on describing everything based on classical notion is probably the cause of a lot of misconception (and apparent trouble) of modern physics[1]. In particular, he picked the outdated idea of "relativistic mass", especially in the teaching of relativity.

The concept of mass in modern physics is quite different from the Newtonian concept of mass as a measure of inertia. However, this does not mean that we should throw out mass as a measure of inertia. Simply modern physics framework is more general and flexible and it explicitly indicates the context under which it is fairly safe to consider the mass as a measure of inertia. The problems begin when things are turned upside down and the Newtonian physics is considered as a basic truth and modern physics as some derivative from it. “Objectivity of Classical physics is some sort of half-truth. It is a very good thing, a very great achievement, but somehow it makes it more difficult than it would have seemed before to understand the fullness of reality”.

There are several things that he mentioned in that article that sounded as if *I* was writing it. So we certainly seem to share the same sentiment with regards to the continuing confusion of modern physics and the various terminologies used.

Last summer you wrote a paper called “Subnanometre Single-Molecule Localization Registration and Distance Measurements.” When asked about it, you said, “I consider it my equivalent of vegging out in front of the TV.”

The first 80 hours a week of my time go to my full-time job at the Department of Energy. But in the wee hours of the morning, on airplane trips, I can go back and forth. It doesn’t take much time, and it’s a good release.

To much fanfare, Italy celebrated 150 years since its unification two weeks ago. Less exuberantly, America is commemorating the 150th anniversary of the outbreak of the civil war, a failed attempt to undo its union. Amid this flurry of historical fissions and fusions it is easy to overlook another, arguably more significant unification set in motion in spring 1861. In March of that year James Clerk Maxwell, a Scottish physicist (pictured above), published the first piece of a four-part paper entitled "On physical lines of force". Sprinkled amid the prose in the Philosophical Magazine were equations which revealed electricity, magnetism and light to be different manifestations of the same phenomenon.

Read the entire article on why this is more than just an important event for the study of electromagnetic theory.

Saturday, April 02, 2011

I mentioned a while back about the Berkeley Earth Group's project that was headed by Richard Muller, that aims to collect an extensive amount of data on the Earth's global temperature. The project and the group are not without controversy (as is the case with something within the area). There are skepticism surrounding the effort, especially considering some of the sponsor of the project. Still, as I wrote in one of the blog entries, I'm still curious to see what they would have come up with.

Let's just say that those who were hoping that Muller's project would debunk climate warming took a severe blow with this one.

There are two separate issues here that should be considered:

1. When you have different studies considering different things, and then they ALL came up with very consistent results (see the graph), it is very difficult not to be convinced of the validity of the conclusion. I'd like to see similar consistencies in results that led to various policies in politics, economics, social sciences, etc.

2. It is of course unfair to simply label Republicans in the US Congress as being "anti-science", or have very little regards for scientific opinions that are contrary to their own beliefs. However, when there is a pattern of disregard, starting from Presidential candidates past and present, and when you think a lawyer, an economist, and a professor in marketing can actually provide meaningful evidence (rather than persuasion) with regards to scientific policies, it is very difficult for me to overlook such a thing and fall into such unfair label for that party. The blatant disregard for the importance (both scientific and economic) of science funding with a catastrophic budget bill proposal simply reinforced such a view.